(Mishnah): If a person wants to prune leaves of vegetables (that are tied into bundles, so they are already obligated in Maaseros) to lighten their load, he should not discard them before separating Maaser (lest an Am HaAretz find them and eat them without tithing).

One who takes (a bundle of) vegetables in the market and he decides to return it, (since it had a fixed price) he should not do so before separating Maaser, because all that it's lacking is counting the number of bundles (as the price had already been fixed and the vegetables had already been taken).

If he was standing and choosing a bundle and then he saw a better bundle, he may return the first one (without tithing), because he did not draw them (into his possession).

(Gemara) (R. Elazar): This Mishnah follows the opinion of R. Meir, who said that they only permitted selling Demai to a wholesaler (who sells in large quantities, so they exempted him from tithing).

(R. Yochanan): (Disagreeing) The Mishnah follows all opinions - this case is different - the owner discarded a large quantity, but the finder only gathered it in small quantities.

Question: Doesn't this disagree with R. Meir, who said that once a person declares something ownerless and it leaves his possession, it is ownerless?

Answer: (It's different here) Since he discarded a large quantity of vegetables, which is not the norm, it does not render it ownerless, so he must tithe it before he discards it.

Question: And doesn't it disagree even with R. Yosi, who said that Hefker does not leave the possession of the owner unless an acquisition is made?

Answer: It is because he made a large quantity Hefker but one who acquires it does it in small quantities, (it is not Hefker and must be tithed before he discards it).

(Chizkiyah): The meaning of the Mishnah's phrase (above (b)) 'She'eino Me'usar Ela Minyan' is 'because all that it's lacking is counting the number of bundles' (in order to pay for his acquisition, since the price per bundle is fixed - therefore, they are already obligated in Maaseros).

What should he do to tithe (without taking away from the bundles)? Take a small amount of leaves from the top of each bundle.

Question: Isn't he stealing (from the seller)?

Answer: It's like the story of R. Shimon bar Kahana and R. Elazar who were walking and R. Shimon was leaning on R. Elazar. They passed by a vineyard and R. Shimon said - 'Bring me a splinter from the tree that is fencing in the vineyard, so that I can pick my teeth'. R. Shimon then said, "Don't bring me anything; because if everyone will do this, there will be no fence left!' (We see here that strictly speaking, it was permitted to take a splinter from there.)

R. Chaggai was once leaning on R. Zeira. Someone passed by carrying a load of twigs. R. Chaggai said to R. Zeira, "Give me a twig to pick my teeth". He then said, "Actually, don't give me anything, because if everyone will do this, his whole load will vanish".

(R. Zeira): (About himself) Don't think that R. Zeira is so upright (that he listened to R. Chaggai) - Hash-m's Torah requires it!

(R. Abahu citing R. Yochanan): (Also understands the word 'Me'user' in the Mishnah to mean lacking) As soon as the person performs an acquisition of Meshicha (drawing the item), he acquires it, since nothing else is lacking except counting it out.

How should it be done? (Disagreeing with Chizkiyah) He should pay the value of one of them and thereby fix up the other bundles.

Question: Doesn't returning them back into the rest of the produce cause those people that come afterwards to stumble?

Answer: He piles them up separately.

Question: Why can't the buyer just return everything and tithe it with his produce at home? Didn't a Tosefta teach that a person may fix his friend's Maaseros with his own, even if he causes a stumbling block for those that follow?

Answer (R. Chinana): They allowed this for a buyer but not for one who is returning produce.

(The Mishnah taught that if he was standing and choosing a bundle and then he saw a better bundle, he may return the first one (without tithing), because he did not draw them (into his possession).) The Mishnah should be understood to mean that he was still selecting the best bundle but hadn't yet taken it. (Therefore he may return it without tithing.)

Question: The Mishnah only spoke about if he saw another better bundle of the same type; what if it was a bundle of a different type of produce? (The Gemara does not answer this question.)